Reconfigurable RF filter

Abstract

A reconfigurable RF filter, which includes a first resonator, a second resonator, and a first coupling circuit, is disclosed. The first coupling circuit is coupled between the first resonator and the second resonator. The reconfigurable RF filter operates in one of a group of operating modes, which include a first operating mode and a second operating mode. During the first operating mode, the reconfigurable RF filter is a bandpass filter having a first bandwidth and a first insertion loss via the first resonator. During the second operating mode, the reconfigurable RF filter is a bandpass filter having a second bandwidth and a second insertion loss via the first resonator, such that the first bandwidth is greater than the second bandwidth and the first insertion loss is less than the second insertion loss.

What is claimed is: 
     
       1. A reconfigurable RF filter, which comprises a first resonator, a second resonator, and a first coupling circuit, which is coupled between the first resonator and the second resonator; wherein:
 the reconfigurable RF filter is configured to operate in one of a plurality of operating modes, such that the plurality of operating modes comprises a first operating mode and a second operating mode; 
 during the first operating mode, the reconfigurable RF filter is a bandpass filter having a first bandwidth and a first insertion loss through the first resonator, the first coupling circuit, and the second resonator; and 
 during the second operating mode, the reconfigurable RF filter is a bandpass filter having a second bandwidth and a second insertion loss through the first resonator, the first coupling circuit, and the second resonator, such that the first bandwidth is greater than the second bandwidth and the first insertion loss is less than the second insertion loss. 
 
     
     
       2. The reconfigurable RF filter of  claim 1  wherein the first resonator and the second resonator are a pair of weakly coupled resonators configured to have a magnetic coupling coefficient that is less than or equal to 0.3. 
     
     
       3. The reconfigurable RF filter of  claim 1  wherein the plurality of operating modes further comprises a third operating mode, such that the first operating mode is a TDD transmit operating mode, the second operating mode is a TDD receive operating mode, and the third operating mode is an FDD operating mode. 
     
     
       4. The reconfigurable RF filter of  claim 1  wherein the first operating mode is a TDD transmit operating mode and the second operating mode is a TDD receive operating mode. 
     
     
       5. The reconfigurable RF filter of  claim 1  wherein the first operating mode is a TDD transmit operating mode and the second operating mode is a TDD receive operating mode, such that during the TDD transmit operating mode, the reconfigurable RF filter is further configured to receive and filter an upstream RF transmit signal via the second resonator to provide a filtered RF transmit signal via the first resonator to an RF antenna. 
     
     
       6. The reconfigurable RF filter of  claim 1  wherein:
 the reconfigurable RF filter further comprises a second coupling circuit; 
 the second resonator is coupled between the first coupling circuit and the second coupling circuit; 
 the first operating mode is a TDD transmit operating mode; 
 the second operating mode is a TDD receive operating mode; and 
 during the TDD transmit operating mode, the reconfigurable RF filter is further configured to receive and filter an upstream RF transmit signal via the second coupling circuit to provide a filtered RF transmit signal via the first resonator. 
 
     
     
       7. The reconfigurable RF filter of  claim 6  wherein the second coupling circuit comprises a groundable and isolable capacitive structure, such that the second coupling circuit is further configured to:
 during the TDD transmit operating mode, receive the upstream RF transmit signal via a connection node; and 
 during the TDD receive operating mode, at least partially tune a frequency response of the second resonator and present about an open-circuit between the connection node and the second resonator, such that a magnitude of a resistance presented by the second coupling circuit between the connection node and the second resonator is greater than 2500 ohms. 
 
     
     
       8. The reconfigurable RF filter of  claim 6  wherein the second coupling circuit comprises an isolable capacitive structure, such that the second coupling circuit is further configured to:
 during the TDD transmit operating mode, receive the upstream RF transmit signal via a connection node; and 
 during the TDD receive operating mode, present about an open-circuit between the connection node and the second resonator, such that a magnitude of a resistance presented by the second coupling circuit between the connection node and the second resonator is greater than 2500 ohms. 
 
     
     
       9. The reconfigurable RF filter of  claim 6  wherein during the TDD transmit operating mode, the reconfigurable RF filter is further configured to have a third insertion loss through the first resonator, the first coupling circuit, the second resonator, and the second coupling circuit, such that the third insertion loss is less than 1.5 decibels. 
     
     
       10. The reconfigurable RF filter of  claim 1  wherein:
 the reconfigurable RF filter further comprises a second coupling circuit and a third resonator; 
 the first operating mode is a TDD transmit operating mode; 
 the second operating mode is a TDD receive operating mode; and 
 during the TDD receive operating mode, the reconfigurable RF filter is further configured to receive and filter an RF receive signal via the first resonator to provide a filtered RF receive signal via the third resonator. 
 
     
     
       11. The reconfigurable RF filter of  claim 10  wherein the reconfigurable RF filter further comprises a third coupling circuit coupled between the first resonator and the third resonator. 
     
     
       12. The reconfigurable RF filter of  claim 11  wherein the third coupling circuit comprises a groundable and isolable capacitive structure, such that the third coupling circuit is further configured to:
 during the TDD transmit operating mode, present about an open-circuit between the first resonator and the third resonator, such that a magnitude of a resistance presented by the third coupling circuit between the first resonator and the third resonator is greater than 2500 ohms; and 
 during the TDD receive operating mode; present about the open-circuit between the first resonator and the third resonator, and at least partially tune a frequency response of the third resonator. 
 
     
     
       13. The reconfigurable RF filter of  claim 11  wherein the third coupling circuit comprises a groundable and isolable capacitive structure, such that the third coupling circuit is further configured to:
 during the TDD transmit operating mode, present about an open-circuit between the first resonator and the third resonator, such that a magnitude of a resistance presented by the third coupling circuit between the first resonator and the third resonator is greater than 2500 ohms; and 
 during the TDD receive operating mode; present about the open-circuit between the first resonator and the third resonator, and at least partially tune a frequency response of the first resonator. 
 
     
     
       14. The reconfigurable RF filter of  claim 11  wherein the third coupling circuit comprises a groundable and isolable capacitive structure, such that the third coupling circuit is further configured to during the TDD transmit operating mode; at least partially tune a frequency response of the first resonator and present about an open-circuit between the first resonator and the third resonator, such that a magnitude of a resistance presented by the third coupling circuit between the first resonator and the third resonator is greater than 2500 ohms. 
     
     
       15. The reconfigurable RF filter of  claim 11  wherein the third coupling circuit comprises an isolable capacitive structure, such that the third coupling circuit is further configured to during the TDD transmit operating mode, present about an open-circuit between the first resonator and the third resonator, such that a magnitude of a resistance presented by the third coupling circuit between the first resonator and the third resonator is greater than 2500 ohms. 
     
     
       16. The reconfigurable RF filter of  claim 11  wherein during the TDD receive operating mode, the third coupling circuit is configured to add a notch filter response to the reconfigurable RF filter. 
     
     
       17. The reconfigurable RF filter of  claim 10  wherein the second resonator is magnetically coupled to the third resonator. 
     
     
       18. The reconfigurable RF filter of  claim 10  wherein the first coupling circuit comprises an isolable capacitive structure, such that during the TDD receive operating mode, the first coupling circuit is configured to present about an open-circuit between the first resonator and the second resonator, such that a magnitude of a resistance presented by the first coupling circuit between the first resonator and the second resonator is greater than 2500 ohms. 
     
     
       19. The reconfigurable RF filter of  claim 10  wherein the filtered RF receive signal is a differential RF signal. 
     
     
       20. The reconfigurable RF filter of  claim 1  wherein the first operating mode is a TDD transmit operating mode and the first coupling circuit comprises a shortable capacitive structure, such that during the TDD transmit operating mode, the first coupling circuit is configured to present about a short-circuit between the first resonator and the second resonator, such that a magnitude of a resistance presented by the first coupling circuit between the first resonator and the second resonator is less than 25 ohms.